Growth in TSMC's 20nm business is expected to continue in the second half of 2015, as the foundry will supply chips for a 4-inch iPhone model tentatively dubbed the iPhone 6C, the sources noted.
The iPhone 6C will be Apple's second (read better) attempt at a budget smartphone to be priced somewhere between $400-500.
Meanwhile, TSMC will supply a portion of processors for the iPhone 6S and 6S Plus models, using its 16nm FinFET technology, the sources indicated.
The sources identify Samsung Electronics as the other processor supplier for the upcoming 6S models. Samsung had long been the sole provider of Apple's A-series chips until it lost out to TSMC for the A8 series used in the iPhone 6 and 6 Plus.